Capacitor microphones may act to transduce the motion of a movable microphone membrane into an electric signal, wherein a fixed electrode, which is usually called a backplate, is typically placed in parallel and in close vicinity to the microphone membrane. Hence, the membrane may move relative to the backplate in response to input sound pressure. This movement may result in a sound pressure dependent variation of the capacitance of this microphone. This variation of the capacitance may be further translated to an electrical signal.
In order to enhance dynamic range of capacitance, comb sensor microphones are known comprising a microphone membrane that may comprise a plate. The plate may be resiliently supported by a fixed member. This structure can be fabricated in MEMS architecture. The membrane can be separated from the surrounding substrate by etching a slit around the perimeter while leaving the connection to the substrate intact, at least at one location of the perimeter.
Interdigitated fingers may be formed both at the membrane as well as the fixed substrate while typically being spaced apart from each other. Hence, a variable capacitance may be established between the moving membrane and the fixed substrate, this capacitance being variable in dependence to the movement of the membrane. Hence, a comb sensor microphone can be fabricated resulting in an in-plane comb sensor structure.